1. Field of the Invention
The invention relates to a method for processing recycled or scrap plastics for the purpose of obtaining raw chemical materials and liquid fuel components, by means of depolymerization of the substances being used, at elevated temperature, to produce both a pumpable and a volatile phase, and separation of the volatile phase into a gas phase and a condensate.
2. Description of the Background
In the depolymerization of recycled or scrap plastics, not only melt-viscous depolymerizate, but also a gas phase and a condensate are obtained, and the condensate must be additionally treated with hydrogenation, because of its chlorine content and low stability. With regard to the state of the art, we refer to the PCT application WO 94/22979.
From the aforementioned document, it is evident that the condensable depolymerization products can be subjected to hydrogenating refining on a solid bed catalyst, or also on a moving catalyst, or a bubbling catalyst bed. Such hydrogenating refining represents normal refining processes, which are also referred to as hydrotreating in the technical literature.
The condensates to be subjected to hydrotreating, however, contain non-evaporating components which come from the depolymerizer, because of foaming, spraying, or vapor inclusions, and also those that have been reformed by means of repolymerization, so that direct charging of a catalyst layer arranged in fixed manner in a hydrotreater would result in rapid inactivation of the same, i.e. would result in very high catalyst consumption. In addition, because of the instability of such condensates, coatings would form on heat exchangers, for example pre-heaters, which would prevent sufficiently long times of operation without interruptions. Document WO 94/22979 teaches converting the condensate, for example by hydrotreating it on commercially available Co--Mo or Ni--Mo catalysts arranged in fixed manner, or introducing it directly into chemical, technical or usual refining processes which tolerate chlorine, as a base substance which contains hydrocarbons (syncrude) (see p. 5), where a prior "guard bed" to extend the useful lifetime of the catalyst layer arranged in fixed manner is also taken into consideration (see page 9, line 7, op. cit.).
From the aforementioned state of the art, the technical teaching of a combination of depolymerization, hydrogenating treatment, preferably of distillate components that have been produced, with sump phase hydrogenation, gasification and/or low temperature carbonization can be derived. Here the task of simplifying the process comes up.
A further task is to prevent rapid inactivation of the catalyst charge of the hydrotreating stage.